sounds as though your car has what is known as "the lurch" , a google search will show many cars using ZF transmissions having the same issue .
I have experienced this a few times on long trips in hot weather whenever I was in stop start highway traffic jams for example queing at the peage (toll booth)on French autoroutes . using the gears in manual mode overcame the lurch .

I thought an additional transmission oil cooler may help because I think the problem is because the transmission is overheating . because I drive mostly short journeys in a cool climate any additional cooler would need a thermostatic regulator to only operate when oil is at max operating temperature. as you live in Florida it may be possible to fit a cooler without the need for a regulator .
some of the more technical dudes on this forum may chime in with their thoughts on this , for or against , the decision to try this is up to you . I would think a sure way to decide is to monitor transmission temp whilst the problem is present .